Hi,
Given a file "test" of size 2342.
The program "Bug.hs" behaves correctly (the result is
"(2048,384)"), but when uncommenting the seemingly innocent
line, the program behaves incorrectly (result is
"(2048,2048)"), and the buffer is filled with garbage.
main =
do han <- openFile "test" ReadMode
arr <- stToIO (newCharArray (0,2048))
n1 <- hGetBufBA han arr 2048
--eof <- hIsEOF han
n2 <- hGetBufBA han arr 2048
print (n1,n2)
I am using solaris and GHC 5.02.1.
Thanks,
/Koen.
module DataStream where
import IO
import IOExts
import MutableArray
import ST
import GlaExts
main =
do dat <- readFileData "DataStream.hs"
writeFileData "copy.hs" dat
------------------------------------------------------------------------
-- Data
newtype Data = MkData [(Int,MutableByteArray RealWorld Int)]
------------------------------------------------------------------------
-- reading, writing
hGetData :: Handle -> IO Data
hGetData han =
do xs <- get
return (MkData xs)
where
get =
unsafeInterleaveIO (
do arr <- stToIO (newCharArray (0,blockSize))
putStrLn "Reading ..."
n <- hGetBufBA han arr blockSize
putStrLn ("(read " ++ show n ++ " bytes)")
--eof <- hIsEOF han
let eof = n /= blockSize
xs <- if eof then return [] else do hIsEOF han; get
return ((n,arr):xs)
)
hPutData :: Handle -> Data -> IO ()
hPutData han (MkData xs) =
sequence_ [ do hPutBufBA han arr n
putStrLn ("(written " ++ show n ++ " bytes)")
| (n,arr) <- xs ]
blockSize :: Int
blockSize = 2048
------------------------------------------------------------------------
-- files
readFileData :: FilePath -> IO Data
readFileData file =
do han <- openFile file ReadMode
hGetData han
writeFileData :: FilePath -> Data -> IO ()
writeFileData file dat =
do han <- openFile file WriteMode
hPutData han dat
hClose han
appendFileData :: FilePath -> Data -> IO ()
appendFileData file dat =
do han <- openFile file AppendMode
hPutData han dat
hClose han
{-
------------------------------------------------------------------------
-- operations
toData :: String -> Data
toData s =
unsafePerformST (
do arr <- newCharArray (0,n)
sequence_ [ writeCharArray arr i c | (i,c) <- [0..] `zip` s ]
return (MkData [(n,arr)])
)
where
n = length s - 1
fromData :: Data -> String
fromData (MkData xs) =
concat (unsafePerformST (sequence [ read n arr | (n,arr) <- xs ]))
where
read n arr =
sequence [ readCharArray arr i | i <- [0..n] ]
(+++) :: Data -> Data -> Data
MkData xs +++ MkData ys = MkData (xs ++ ys)
------------------------------------------------------------------------
-- helpers
unsafePerformST :: ST RealWorld a -> a
unsafePerformST m = unsafePerformIO (stToIO m)
-}
------------------------------------------------------------------------
-- the end.
module Main where
import IO
import IOExts
import MutableArray
import ST
import GlaExts
main =
do han <- openFile "test" ReadMode
arr <- stToIO (newCharArray (0,2048))
n1 <- hGetBufBA han arr 2048
--eof <- hIsEOF han
n2 <- hGetBufBA han arr 2048
print (n1,n2)
